1. Technical Field
The present invention relates to a cavity noise reduction tire, more particularly to a cavity noise reduction tire having a ratio of the cross-sectional area of the sound-absorbing material to the cross-sectional area of the space formed by the internal surface of the tire which is to be about 23-29%.
2. Description of the Related Art
Generally, a pneumatic tire is being used with air filled therein in order to absorb vibrations caused by uneven road surfaces, thereby increasing durability of the vehicle and providing a comfortable ride to passengers. In a tire, a tread pattern comprising a plurality of dimples and grooves is formed on the tread portion which is to be in contact with the road surface, thereby enhancing the steering and driving capabilities of the vehicle.
However, when the vehicle is being driven, the tire is excited according to the curvature and the surface of the road, and the excited tire causes turbulence in the air inside (the tire cavity) of the assembly comprising the wheel and the tire. The turbulence in the air inside of the assembly comprising the wheel and the tire causes a noise. The space, which is formed by the assembly comprising the wheel and the tire, functions as a resonance box causing a resonance phenomenon, thereby amplifying such noise further.
The resonance frequency associated with a tire structure has a specific frequency of the tire corresponding to the integer multiples of the speed of sound divided by the length of the circumference of the air layer.
In Korean Patent Application Publication No. 2008-0070862, Japanese Patent No. 5078907, Japanese Patent No. 3727024, Japanese Patent No. 3974437 and the like, positioning of a sound-absorbing material inside of a tire is suggested for reducing the noise caused by the resonance.
In addition, a tire is being driven under the very harsh environmental conditions. Continuous impact, bending and stretching are occurring, and also the tire operating temperatures are various such as high temperature, room temperature, and low temperature. For example, when braking and accelerating the vehicle, the tire temperature tends to increase rapidly, while the temperature is maintained at a constant level during normal driving, and the tire temperature is low in a season like winter.
In Korean Patent Application Publication No. 2011-0042068, sound-absorbing materials having elasticity values of 4-15% are described. However, it is described that the visco-elasticity performance of such sound-absorbing material is consistent at the high temperature between 70° C. and 80° C. but in a low temperature, a foaming agent of different chemical material must be used, thereby implying that the visco-elasticity cannot be maintained at a low temperature.
In addition, in Japanese Patent Nos. 3787343 and 4330550, it is described that the durability of the sound-absorbing material can be enhanced by making the tensile strength in the range of 70 kPa to 120 kPa, or 70 kPa to 160 kPa. However, only application of the double-sided adhesive tapes having high peel strength (splitting resistance) at room temperature and high temperatures for such sound-absorbing materials is described, but any means for enhancing the adhesive strength at lower temperatures are not described.
Thus, since the studies on adhesion capability and durability of the conventional sound-absorbing materials for a tire with reduced cavity noise are not sufficient, it is quite common that the sound-absorbing material is peeled as the stress is focused on the bonded interface due to the deformation caused by the vibration of the tire, or the sound-absorbing material is damaged due to the external temperature.
Moreover, although it is disclosed in Japanese Patent No. 3622957 that the ratio of the volume of the sound-absorbing material to the total volume of the tire inner cavity is to be more than 0.4% in order to enhance sound-absorption capability, there is a problem of degradation in durability due to the heavy compressed deformation at the top area of the sound-absorbing material corresponding to the height thereof.
In addition, it is disclosed in Japanese Patent No. 3964878 that the ratio of the volume of the sound-absorbing material to the total volume of the tire inner cavity is to be 0.4-20%, however, there is a problem that the sound-absorption capability cannot be maximized.